One technique currently receiving attention in the art achieves small dimensions and precise positioning by defining a vertical positioning location or line on the planar surface of the device substrate, angularly depositing conductive material or metal against the face of the vertical line which provides a thicker deposit against the face than on the horizontal and then removing the deposited material on the horizontal leaving the vertical portion of the deposited material. This technique achieves smaller dimensions than are directly attainable with the tolerances of the individual operations.
Very small dimensions have been achieved using the angular deposition technique applied under the developed overhang of a photoresist. This technique is described in the Journal of Vacuum Science and Technology, Vol. 19, No. 3, Sept./Oct. 1981, page 693. In this prior art technique, an undercut photoresist edge is provided with a metal film that is deposited at a low angle with respect to the substrate. The resulting metal film is thicker on the sidewall than on the horizontal surface. Thereafter, a metal etch can be used to remove the metal from the horizontal surfaces while leaving the metal on the photoresist sidewall. Lines with lengths as small as 600 .ANG. are reported.
The angular deposition procedure however has certain disadvantages. Where the electrode being made has some length, the line quality is dependent on the quality of the resist edge against which the angular deposition took place. The resist is usually in photoresist. Defects in the quality may cause breaks. If low resistance is required, then it is necessary to make the aspect ratio, which is the height with respect to the width, large and this in turn makes a high but marginally supported line vulnerable to damage. Further connections to such a small line are difficult.